全文获取类型
收费全文 | 60431篇 |
免费 | 3252篇 |
国内免费 | 2663篇 |
专业分类
化学 | 28968篇 |
晶体学 | 246篇 |
力学 | 2424篇 |
综合类 | 776篇 |
数学 | 20148篇 |
物理学 | 13784篇 |
出版年
2024年 | 141篇 |
2023年 | 1003篇 |
2022年 | 1727篇 |
2021年 | 1997篇 |
2020年 | 2365篇 |
2019年 | 2140篇 |
2018年 | 1731篇 |
2017年 | 1681篇 |
2016年 | 1839篇 |
2015年 | 1681篇 |
2014年 | 2340篇 |
2013年 | 5972篇 |
2012年 | 2321篇 |
2011年 | 2188篇 |
2010年 | 1978篇 |
2009年 | 2647篇 |
2008年 | 2875篇 |
2007年 | 2979篇 |
2006年 | 2316篇 |
2005年 | 1715篇 |
2004年 | 1515篇 |
2003年 | 1581篇 |
2002年 | 3967篇 |
2001年 | 1659篇 |
2000年 | 1214篇 |
1999年 | 1043篇 |
1998年 | 1047篇 |
1997年 | 774篇 |
1996年 | 764篇 |
1995年 | 668篇 |
1994年 | 636篇 |
1993年 | 660篇 |
1992年 | 639篇 |
1991年 | 440篇 |
1990年 | 377篇 |
1989年 | 339篇 |
1988年 | 375篇 |
1987年 | 279篇 |
1986年 | 285篇 |
1985年 | 393篇 |
1984年 | 314篇 |
1983年 | 203篇 |
1982年 | 359篇 |
1981年 | 544篇 |
1980年 | 504篇 |
1979年 | 519篇 |
1978年 | 423篇 |
1977年 | 335篇 |
1976年 | 282篇 |
1973年 | 198篇 |
排序方式: 共有10000条查询结果,搜索用时 437 毫秒
91.
本文应用上、下解方法和 Leray-Schauder不动点定理 ,证明了一类拟线性椭圆方程边值问题弱解的存在性 ,并且给出了一个应用实例 相似文献
92.
Robert S. Strichartz 《Proceedings of the American Mathematical Society》2002,130(3):805-817
Harmonic mappings from the Sierpinski gasket to the circle are described explicitly in terms of boundary values and topological data. In particular, all such mappings minimize energy within a given homotopy class. Explicit formulas are also given for the energy of the mapping and its normal derivatives at boundary points.
93.
Let G=(V(G),E(G)) be a graph. A (n,G, λ)‐GD is a partition of the edges of λKn into subgraphs (G‐blocks), each of which is isomorphic to G. The (n,G,λ)‐GD is named as graph design for G or G‐decomposition. The large set of (n,G,λ)‐GD is denoted by (n,G,λ)‐LGD. In this work, we obtain the existence spectrum of (n,P3,λ)‐LGD. © 2002 Wiley Periodicals, Inc. J Combin Designs 10: 151–159, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jcd.10008 相似文献
94.
A FUNDAMENTAL SOLUTION FOR THE LAPLACE OPERATOR ON THE QUATERNIONIC HEISENBERG GROUP 总被引:2,自引:0,他引:2
朱理 《数学物理学报(B辑英文版)》2002,22(3)
In this paper, the author studies the Laplace operator on the quaternionic Heisenberg group, construct a fundamental solution for it and use this solution to prove the Lp-boundedness and the weak (1-1) boundedness of certain singular convolution operators on the quaternionic Heisenberg group. 相似文献
95.
本文利用聚集型状态方程,克拉贝龙方程以及临界条件推出聚集活性参量方程.分析结果表明,医药的药理活性是可以用聚集活性参量予以定量表征.本文给出了某些医药的主要的药物成分,如氧化亚氮 乙醚、氯仿和水杨酸甲酯等嘛醉剂),一氧化氮(硝酸甘油)、乙醇胺(医药活性剂)和多巴胺(神经递质)的生物活性数据.实践经验表明,这些化学品分别在生命体的心血管系统、神经系统和免疫系统中起着重要的药理功能作用.这表明,本文研究的内容在医药学研究领域有其重要意义. 相似文献
96.
97.
Ludmila C. Fidale Sarah Köhler Martin H.G. Prechtl Thomas Heinze Omar A. El Seoud 《Cellulose (London, England)》2006,13(5):581-592
The concentrations of water, W, and electrolytes present in solutions of LiCl in N,N-dimethylacetamide, LiCl/DMAc, and of tetrabutylammonium fluoride. x-hydrate in DMSO, TBAF.xW/DMSO can be accurately and expediently determined by three independent methods, UV–vis, FTIR and EMF measurement. The first relies on the use of solvatochromic probes whose spectra are sensitive to solution composition. It is applicable to W/LiCl/DMAc solutions but not to TBAF.xW/DMSO, because the charge-transfer complex bands of the probes are suppressed by strong interactions with the latter electrolyte. Integration of νOH band of water may be employed in order to determine [W], hence [electrolyte] by weight difference. EMF measurement uses ion-selective electrodes in order to determine [electrolyte], hence [W] by weight difference. Results of the latter method were in excellent agreement with those of FTIR. The reason for the failure of Karl Fischer titration is addressed, and the relevance of the results obtained to functionalization of cellulose under homogenous solution conditions is briefly commented on. 相似文献
98.
P. E. Cladis 《Journal of statistical physics》1991,62(5-6):899-925
We first discuss nonlinear aspects of phase transition theory applied to a particular liquid crystal phase transition. A simple derivation is given to show how two coupled Goldstone modes (one appearing as gauge fluctuations of the ordered phase) can force a phase transition, against all expectations, to take place discontinuously (theory of Halperin, Lubensky, and Ma)-but the discontinuity may be immeasurably small. Then, we describe a new dynamical test of phase transition order, developed by Cladiset al., that turns out to be more sensitive than x-ray diffraction and adiabatic calorimetry. Quantitative data found by this new method are in excellent agreement with the measurements of adiabatic calorimetry and x-ray diffraction as well as expectations implicit in the predictions of HLM.This is the text of an after-banquet talk given at the CNLS Workshop on the Dynamics of Concentrated Systems. 相似文献
99.
Summary In this paper a Gauss-Jordan algorithm with column interchanges is presented and analysed. We show that, in contrast with Gaussian elimination, the Gauss-Jordan algorithm has essentially differing properties when using column interchanges instead of row interchanges for improving the numerical stability. For solutions obtained by Gauss-Jordan with column interchanges, a more satisfactory bound for the residual norm can be given. The analysis gives theoretical evidence that the algorithm yields numerical solutions as good as those obtained by Gaussian elimination and that, in most practical situations, the residuals are equally small. This is confirmed by numerical experiments. Moreover, timing experiments on a Cyber 205 vector computer show that the algorithm presented has good vectorisation properties. 相似文献
100.
This paper reports that the m-plane GaN layer is grown on (200)-plane LiAlO2 substrate by metal-organic chemical wpour deposition (MOCVD) method. Tetragonal-shaped crystallites appear at the smooth surface. Raman measurement illuminates the compressive stress in the layer which is released with increasing the layer's thickness. The high transmittance (80%), sharp band edge and excitonic absorption peak show that the GaN layer has good optical quality. The donor acceptor pair emission peak located at -3.41 eV with full-width at half maximum of 120 meV and no yellow peaks in the photoluminescence spectra partially show that no Li incorporated into GaN layer from the LiAlO2 substrate. 相似文献